Pressure responsive instrument



Sept. 17, 1940. P. KOLLSMAN 2,215,448

I PRESSURE RESPONSIVE INSTRUMENT Filed may 6, 1938 2 Sheets-Sheet l FIGJ.

INVENTOR W KM Sept. 17, 1940.

P. KO LLSMAN PRESSURE RESPONSIVE INSTRUMENT 2 SheetS-Sheet 2 Filed May 6, 1938 INVENTOR WWW -- Patented Sept. 17, 1940 I UNITED STATES PATENT OFFICE PRESSURE RES PONSIVE INSTRUMENT Paul Kollsman, New York, N. Y., assignor, by

mesne assignments, to Square D Company, Detroit, Mich., a corporation of Michigan Application May 6, 1938, Serial-No. 206,402

3 Claims. (Cl. 264-1) This invention relates to improvementsinpresinvention will appear from a consideration of sure responsive instruments, more particularly the description and the. accompanying drawto improvements in instruments responsive to the ings showing for purely illustrative purposes emrate of a pressure change. Instruments of the bodiments'of this invention. It is to be underlatter kind are known in the aircraft field as stood, however, that the description is not to be 5 rate of climb or vertical speed indicators. taken in a limiting sense, the scope of this in- In pressure responsive instruments, and rate vention being defined in the appended claims.

of pressure change responsive instruments in par- Referring to the drawings: ticular, it was observed that instruments show Figure l is a sectional enlargement of a vera considerable error if subject to changes in temtical speed indicator for aircraft. 10 perature caused by a one-sided or local heating Figure 2 is a front view partly in section of of the instrument, a temperature error which the instrument shown in Figure 1. cannot be compensated for by means of the usual Figure 3 shows in part a modified form of temperature responsive element included in the the instrument shown in Figure 1.

mechanism of the instrument. In instrument casing it] having a mounting 15 It is accordingly an object of this invention to flange H is provided with an aperture I2 closed provide an improved instrument in which the by a window l3 held in place by means of a snap operating mechanism is temperature insulated. ring I4. A vacuum bottle l5'closed by means of Rate of pressure change responsive instrua stopper l6 suitably of compressed cork or simiments usually operate on the principle of measlar temperature insulating material provides a uring the differential pressure between a point pressure chamber l'l. subject to changes in pressure and an enclosed Inside the pressure chamber a pressure responvolume of gas or air communicating with said sive element shown in the illustrated example point through a constricted passage. In order as being a diaphragm capsule I8 is provided,

I to maintain low the temperature error caused actuating a rotatable shaftlfl mounted in bearby changes in. temperatureof the enclosed air ings 20 and 2| by means of a link 22 pivotallyor gas volume, it has become customary to enconnected to the capsule at 23 and a crank memclose the said air or gas volume within a chamber 24 secured to the shaft I9. ber formed partly or entirely of a vacuum bottle. For purposes of zero adjustment the diaphragm I According to this invention, I propose to encapsule is preferably adjustable mounted with close the operating mechanism of a rate of presrespect to the actuating mechanism operated sure change instrument within the same vacuum thereby. In the illustrated embodiment the capbottle containing the volume of air from which sule I8 is mounted on a cantilever member 25, one pressure for the measurement is derived. mounted at 26 to a support 21, the support be- This novel arrangement, besides providing a teming positioned with its base plate 28 at the in- 5 perature protection for the operating mechanism side of the stopper IS. A shaft 29, having an of the instrument, serves a further purpose: as eccentric portion 30, is rotatably mounted in the the volume of the operating parts of a rate of base plate 28 andtightly fitted in the stopper pressure change responsive instrument is rela- Hi to prevent pressure leakage. The eccentric tively small but requires considerable space, it is portion engages the free arm 3| of the cantipossible by the novel arrangement considerably lever member 25, thereby permitting upon rotato increase the magnitude of the enclosed gas tion of the shaft 29 a positional adjustment of or air volume by making the vacuum bottle large the capsule l8 relatively to the shaft l9.

enough also to include the, operating mecha- For rotating the shaft 29 from the outside, a nism. train of gears is shown comprising a spur gear It is thus a further. object of this invention to 32 secured to the shaft 29 meshing with a secprovide a rate of pressure change instrument 0nd gear 33 rotatable about a' pivot 34 in a front having a greater accuracy by using a greater volplate 35. The second gear 33 meshes with a pinume of enclosed air or gas without enlarging ion 36 rotatable with its screw-headed shaft 31 s the overall dimensions of the instrument. This -in the casing l0.- 5

advantage is of particular importance for ver- Indicating means are provided shown in the tical speed indicators for aircraft where great illustrated embodiment as being a pointer 38 roaccuracy combined with small dimensions of tatable with its shaft 39 relatively to a dial 40, the instrument are required. 4 shown as secured to the front plate 35 by means Further aims, objects and advantages of this of screws 4|. v

The pointer shaft in the illustrated embodiment is supported for rotation in a tubular member 42 having a flange 43 for mounting on the base plate 28 and mounting jewel bearings 44 and 45. The shaft 39 in this embodiment is well fitted in the front bearing 44 as to prevent undue pressure leakage through the'bearing while, at the same time, ofiering a minimum of friction to the shaft. A pinion 46 secured to or integral with the shaft 39 meshes with a toothed segment 41 secured to the shaft i9 at 48. For the purpose of imparting a bias to the capsule l8 or for removing lost motion in the operating mechanism a spiral spring may be employed in the conventional manner as indicated in the drawings at 49.

The interior of the diaphragm capsule I8 is connected through a conduit 50 to the interior space of the casing outside the vacuum bottle I5, the conduit 50 terminating at 5|. The interior of the bottle I1 is connected with the space inside the casing l through a constricted passage in the illustrated embodiment shown as being capillary tube 52 .located inside the vacuum bottle to assume the temperature prevailing therein and terminating at 53.

In order to obtain a tight sealing of the space I! from the interior of the casing H], a rubber gasket 54 may be provided in addition against which the bottle I is firmly held by means of a compression spring 55 between the bottle and the bottom of the casing.

The operation of the device is as follows: Upon a change in pressure inside the casing It) the relatively small volume of air or gas inside the diaphragm capsule I 8 will instantaneously assume the changed pressure value by virtue of its connection through the conduit 50. tively large volume enclosed within the vacuum bottle I! follows the pressure change only very slowly on account of the resistance ofiered by the constricted conduit 52 to a flow of gas or air flowing therethrough. Accordingly a pressure difierential is created acting on the diaphragm capsule which causes the pointer to be deflected a certain amount. Obviously if the change in pressure is sudden and great, the deflection of the pointer will be great in response to a relatively great differential pressure acting on the diaphragm capsule. If, on the other hand, the pressure inside the casing I0 changes very slowly, the corresponding flow of air or gas through the constricted conduit will be small and the pressure differential acting on the diaphragm capsule will be small. This results in a small deflection of the pointer.

For determining the change in pressure at a distant point, for example at the outside of an airplane, a pressure line may be connected to the casing II) which is shown as having a threaded bushing 56 for connection of a pressure line thereto. A groove 51 in the wall of the casing may be provided as a low resistance passage between the pipe connection 56 and the front part of the casing in which the conduits 50 and 5 terminate.

In the illustrated embodiment a relatively small leakage occurs through the pointer bearing 44. As this leakage is small but of constant magnitude it can easily be taken into consideration when designing the calibration of the dial. In eifect -the leakage at the bearing-44 acts like a second constricted conduit connecting the interior space of the vacuum bottle with the interior of the casing.

Figure 3 shows a modified form of the inven- The relation in which any leakage at the pointer shaft is prevented. The vacuum bottle I5 is sealed by means of a stopper I6 preferably of compressed cork or the like having a thin walled portion 58 preferably of thin metal or molded material thus providing a tight closure of the space inside the bottle. The segment 41 on the shaft l9 meshes with a pinion 46 secured to or integral with a shaft 39' mounted in bearings 44' and 45' in a tubular member 42'. Concentric with the shaft 39' a pointer shaft 39" is provided carrying the pointer 38 and rotable in bearings 44" and 45 in a tubular member 42". The two shafts 39' and 39" are connected for joint angular motion by means of magnetic elements 59 and 60 secured to the respective shafts. When the shaft 39' and the element 59 are rotated the shaft 39" and the member 60 will repeat this movement by virtue of the magnetic coupling of the elements 59 and 60.

Obviously the present invention is not restricted to the particular embodiments herein shown and described. Moreover, it is not indispensable that all the features of this invention be used conjointly since they may advantageously be employed in various combinations and subcombinations.

What is claimed is:

1. A rate of pressure change responsive instrument comprising, in combination, an instrument casing; a transparent window fitted into said casing; a dial visible through said window; a pointer movable relatively to said dial; a vacuum bottle inside said casing; a stopper sealing the inside of said bottle from the inside of said casing and supporting said dial at the one side; a support mounted on the other side of said stopper and inside the space of said bottle; a diaphragm capsule carried by said support; a conduit passing through said stopper and connecting the inside of said capsule with the inside of said casing; a capillary tube passing through said stopper and connecting the inside of said bottle with the inside of said casing; a tubular bearing member passing through said stopper; a pointer shaft and a pinion integral therewith mounted in said bearing member said shaft supporting said pointer; a toothed sector pivotally mounted on said support to mesh with said pinion; a link connecting said capsule and sector for actuation of said sector in response to movements of said capsule; and means for connecting the inside of said casing to a source of pressure the rate of change of which is to be determined.

2. A rate of pressure change responsive instrument comprising, in combination, an instrument casing; a transparent window fitted into said casing; a dial visible through said window; a pointer movable relatively to said dial; a vacuum bottle inside said casing; a stopper sealing the inside of said bottle from the inside of said casing and supporting said dial at the one side; a support mounted on the other side of said stopper and inside the space of said bottle; a diaphragm capsule; a cantilever spring supporting said diaphragm and mounted on said support; a shaft rotatable from the outside passing through said stopper and having an eccentric portion bearing against the free arm of the cantilever spring, thereby permitting positional adjustment of said capsule; a conduit passing through said stopper and connecting the inside of said capsule with the inside of said casing; a capillary tube passing through said stopper and connecting the inside of said bottle with the said support to mesh with said pinion; a link.

connection connecting said capsule and sector for actuation of said sector in response to movements of said capsule; and means for connecting the inside of said casing to a source of pressure the rate of change of which is to be determined,

3. A pressure change responsive instrument comprising, in combination, a substantially cylindrical instrument casing; a supporting member insertable into said casing; a diaphragm capsule and a motion amplifying mechanism connected to said capsule mounted to one side of said supporting member; a temperature insulating vessel air tightly sealed against and supported by said supporting member to form an air chamber therewith enclosing saidcapsule and mechanism; indicating means mounted to the other side of said support; a motion transmitting means for actuating said indicating means from said mechanism through said support; and means providing a constricted passage through said support to connect said chamber with the surrounding atmosphere, whereby said supporting member,

from said instrument casing.

PAUL KOLLSMAN. 

